Winter vs Summer Solar: Why Output Drops and What to Do

Solar output in winter can be half or less of summer in southern Australia. For off-grid systems, winter is the season to design for.

1. Why winter is lower

• Shorter days.
• The sun is lower, so light comes through more atmosphere and hits panels at a steeper angle.
• More cloud in many areas.
• Longer shadows.

2. Peak sun hours

Solar output is often estimated in peak sun hours (PSH), the equivalent hours of full sun. As a rough idea, many southern areas get somewhere around 2 to 3 PSH in mid-winter and 6 or more in summer. Look up figures for your town.

3. Planning for it

• Size off-grid arrays using winter PSH.
• Tilt panels steeper to favour the low winter sun.
• Plan a generator for long cloudy spells.
• Cut winter loads: efficient heating, LED lights, timers.

4. Grid-tie systems

With grid-tie, winter just means buying more from the grid. Check your yearly bill, not just the summer quarter.

5. Quick summary

• Winter output can be half of summer or less.
• Design off-grid systems for winter.
• Tilt steeper and have backup.
• Try the Winter Solar Shortfall Calculator.

In Australia, any work on 240V AC wiring, including connecting an inverter, battery or solar system to a switchboard or fixed wiring, must be done by a licensed electrician.

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